New Scan Spots Beginning of Bone Problems in Anorexics

Structural abnormalities start early, researchers report

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"What we have found in this study is an exciting new thing," said Dr. Miriam A. Bredella, lead author of a report in the December issue of Radiology. "Prior studies have shown only decreased bone density. We show abnormalities of bone structure. Our data suggest that tests showing normal values of bone density in these adolescents do not reflect the true status of bone structure."

The new study "shows that the quality of bone in women with anorexia is not normal, which is something we have suspected for a while, because they fracture even with normal bones," said Dr. Michelle Warren, a professor of medicine and obstetrics and gynecology at Columbia University, who has done studies of her own on the subject.

"This CT methodology is new and gives better knowledge about what is going on in the bones, because it gives information about their architecture," Warren said.

In terms of medical treatment of women with anorexia, "it shows that we really should pay more attention not only to the absolute value of the bones, but also to how much weight an individual has lost," she said.

Anorexia is characterized by a distorted body image and intense fear of gaining weight that leads to dangerous food deprivation. It occurs primarily in young women, affecting perhaps one of every 100 adolescent girls, according to the U.S. National Women's Health Information Center.

Bone studies in anorexia typically use X-rays. The newly reported research used a technique called high-resolution, flat-panel volume computer tomography to compare the bones of 10 girls, aged 13 to 18, with mild anorexia with those of 10 age-matched girls without the eating disorder.

"This is a CT scan that makes very thin slices of bone to see bone structure," said Bredella, who is an assistant professor of radiology at Harvard Medical School and a musculoskeletal radiologist at Massachusetts General Hospital. "It uses a low dose of radiation, about the same as from the background radiation over a three-day period."

The CT scans showed no significant difference in bone mineral density in the two groups. They did show significant structural differences, indicating that the first bone problems in anorexia begin before changes in bone density can be detected.

Early detection of bone problems is desirable, because "deficits in adolescence result in low peak bone mass and increased risk of fracture in adult life," Bredella said. "It can be done with a modality that evaluates bone structure as well as density."

Tests to detect changes in bone structure might be done "if an adolescent has the disease for a while, and it is not getting better," she said. While the flat-panel volume CT scan used by her group is not widely available, other CT scans in wide clinical use can detect bone structure abnormalities, Bredella said.

There are established treatments, such as low-dose testosterone, that can be used to treat bone disorders in anorexia, she said.